CLEE HILL LAGS TRAIL REPORT...16th AUGUST 2016 Map ref. OS Explorer Series Sheet 203 Ludlow (1:25 000 scale)

Our August trail got off to a fine start, there were clear blue skies and it was a warm and sunny morning. We left Malvern at around 9am and headed for Clee Hill, a fine hot summer's day was forecast - a day to bring out our hats, shorts and shades. However, when we arrived at the car park in Clee Hill village SO 595753, near the summit on the A4117 at 380 metres, there was a cool breeze and a distinct chill in the air. But this was ideal for walking on the geological trail.

There were nine members of the Landscape Appreciation Group LAGS who gathered around Richard Edwards who was to be our guide assisted by Janet Parry. Richard outlined what we would see on the trail. It was to be a circular walk around the west side of the Clee Hills, we would see; a disused quarry, a working quarry, abandoned industrial areas and magnificent distant views of the surrounding countryside. Satellite Image of the Clee Hills showing points of interest on the trail. The Geology Outlined.

Refer to the geological map and section at the end of the report.

Richard explained that the geology in South Shropshire, was quite different to that which we had seen on previous trails. Looking south across the low-lying landscape towards the Malverns the underlying rock belongs to the Pridoli sub-division of the Silurian. The sediments were laid down in continental conditions because of uplift which represents an early phase of the Caledonian orogeny. The marine Silurian rocks ,consisting of siltstones and limestones, usually form positive features such as Hergest Ridge and the Woolhope Dome. In contrast the Pridoli sedimentary rocks are more easily eroded. The Caledonian Orogeny began towards the end of the Silurian with its climax in the Devonian. This resulted in the building of a great mountain chain, stretching for thousands of miles in length, and signalled the change from marine to continental conditions.

The rapid erosion of the mountains provided the sediment for the Old Red Sandstone of the succeeding Devonian Period which underlies much of Herefordshire to the southwest.

This was followed by the Carboniferous Period and deposition of the Coal Measures which were formed around Clee Hill. The Coal Measures consist of mudstone, siltstone and sandstone horizons with seat earths and coal seams - see geological section. Titterstone Clee and Clee Hill are part of an outlier of Carboniferous sedimentary rocks.

The end of the Carboniferous saw the onset of the Variscan Orogeny and the intrusion of a dolerite sill, which forms the Clee Hills and caps Brown Clee Hill, to the northeast, they are on the Caledonian trend. The Clee Hills are outliers; newer rocks surrounded by older rocks of the Devonian and Silurian Periods.

Dolerite is a medium grained dark basic igneous rock, mineralogically and chemically the same as the coarse grained rock gabbro and the fine grained basalt.

This whole area is a dream location for any industrial archaeologist. Since the Middle Ages deposits of coal, clay, ironstone, limestone, building stone and roadstone have been exploited and these industrial activities have left their mark on the landscape.

In the car park we are standing on the Carboniferous Cornbrook Sandstone Formation, a coarse grained, pebbly sandstone and mudstone. From the car park we crossed the A4117 and took the track heading north past the Kremlin public house to a gate on the right and the footpath which led us to the observation point for the Incline Quarry. Point B. (SO 5955 7565)

We are now standing on dolerite. The dolerite was intruded in the late Carboniferous Period when a silica-poor magma forced its way from depth towards the surface between the Carboniferous sandstones and shales to spread laterally as a thick layer to form a dolerite sill.

The sill is now exposed in the quarry, the columnar structure in the dolerite has formed as a result of contraction of the dolerite as the sill cooled and solidified. This could be clearly seen in the exposure on the high back wall of the quarry. Richard said that the effect is similar to that seen in the columnar jointing in the basalt columns of The Giants Causeway. The rock is an olivine dolerite, which is determined by its mineral composition (its local name is Dhustone). Above the olivine dolerite sill there is a layer of horizontal Carboniferous Coal Measures - sandstones and dark grey shales. These rocks were baked hard by a process known as contact metamorphism and they provide a protective cap for the dolerite sill. Richard said that metamorphism is something that we had not come across before on previous trails and explained that the sandstones were metamorphosed by the intense heat from the intruding magma.

The contact between the horizontal layers of the metamorphosed Carboniferous Coal Measures and the Olivine Dolerite sill can be clearly seen in the high wall of Incline Quarry.

Richard told us that due to chemical weathering the dolerite decomposes faster than the sandstones. A quartz-rich sediment like sandstone has a high resistance to chemical attack when exposed to weathering agents at or near the ground surface; in contrast the chemical stability of a basic magma like dolerite, formed at high temperatures at depth, is considerably lower when exposed to weathering agents. Richard also said that dolerite was a good road building stone but it was not used today for road surfacing because it has a low polished stone value. Dolerite has been used in the past for paving the streets of Victorian towns in the form of setts; these were small rectangular blocks. The nature of the vertical and horizontal jointing in the dolerite allowed it to be split in all directions to produce the blocks. Carline Thistles were growing in the gravel around the observation point.

We retraced our steps to the gate and down the path to the incline trackway. We then followed the old trackway in a northwesterly direction, past many industrial relics. The trackway runs over several faults, we first walked over a narrow band of basal sandstone in the Coal Measures (sa), then onto the olivine dolerite sill (D) before coming onto the Lower Coal Measures (LMC). We left the trackway and walked past the quarry workers cottages and turned right uphill on the access road to Titterstone Clee, still on the Lower Coal Measures. Soon we took a right turn onto a footpath and up the steps, again on the dolerite, to the viewing area for Dhustone Quarry SO 5918 7635. Point C. (SO 5918 7635)

Panoramic view of Dhustone Quarry. The Malvern Hills are on the horizon just to the left of the aerial mast and the weathered dolerite sill is near the right of the picture.

Weathered Dolerite Sill This is an active quarry extracting dolerite. Richard commented on how well the quarrying operations were concealed from view and how the area was being re-landscaped using quarry waste. This is described in detail on the information board. Richard drew our attention to a large section of weathered dolerite on the right of the picture, this eroded section had no cover of the Coal Measures.

We retraced our steps down to the middle viewing area display board, Janet came prepared for the job and cleaned off the board. Here we had views to the north, with Titterstone Hill in the foreground and with distant views of the Shropshire hills around Church Stretton.

Janet pointed out the Long Mynd Hills near Church Stretton and Caer Caradoc which is further north on the east side of the A49 road to Shrewsbury.

At the lower viewing area display board with the Ludlow anticline left of centre. At the lower viewing area display board, we had fine views over Ludlow with the higher ground of Mortimer Forest beyond and the Welsh Mountains on the horizon. Richard explained that William Smith had named the rocks around Ludlow as the Transition Series. It was Roderick Murchison and Adam Sedgwick in the 1830's, who decided to sort this out, although there was much controversy. It was Murchison, who described the rocks in this area, and named it the Silurian, after a Welsh tribe the Silures.

Richard pointing out the Silurian Limestones of the Ludlow anticline on the geological map, it can be seen in the centre of the picture above the map.

The hills behind Ludlow are an expression of the asymmetrical Ludlow anticline. The Ludlow anticline is outlined by the Mortimer Forest where the Silurian Limestones have resisted erosion. This folded sequence of strata extends northeast and passes between Titterstone Clee and Brown Clee. The Upper Marine Silurian limestones are more resistant to erosion than the mudstones and form the high ground of Mortimer Forest. We returned on the path and took the steps down to the tarmac road, there were many spoil heaps around here and terracing due to slumping was evident.

We walked up the tarmac road and took a path off to the left just before Benson's Brook at Horseditch. Here at Point D (SO 5953 7727), we had our picnic lunch with fine views of the surrounding countryside out to the west. Growing in the damp conditions on the bank of the brook we saw several Bay Willow trees (Salix pentandra), this is a northern tree and must be on the southern limit of its range, exposed high up on Clee Hill.

Near this point can be found evidence of the outcrop of the Coal Measures sequence, although we did not see this on the trail. The sediments have been described as coal-bearing but consist mainly of thick seat earths and sandstones with conglomerates, but there are occasional traces of coal and grey mudstones with ironstone nodules. The spoil heap from an old bell pit of medieval coal workings is visible on the south side of the stream.

The Coal Measures comprise a sequence of sedimentary rocks; shales mudstones and sandstones and four recognised coal seams. Coal mining on the Clee Hills is recorded as early as 1235 and by the beginning of the 18th century a large number of 'Bell Pit' workings existed. On the descent from Titterstone Hill, the Ludlow anticline can be seen in the centre of the picture.

After lunch we returned to the road and crossed the brook and took the bridleway heading west downhill, sand spurrey was growing on the gravel track. We continued down the track, moving off the Coal Measures onto the Devonian St. Maughan's Formation (SMg), until we joined the Shropshire Way, we then turned right heading towards Titterstone Incline. We climbed onto the embankment near a bridge over the bridleway. Point E. (SO 5882 7743)

LAGS on location – Titterstone Incline. The embankment for the incline railway was built in 1880 to take away much of the quarried stone which was worked in Victorian times primarily for pavement setts, whereas it was used for roadstone in the 20th Century. The quarry at Titterstone opened in 1881. It is a prominent excavation in the olivine dolerite sill and it has a similar composition to the sill exposed in the Incline Quarry but the two areas are separated by Coal Measures strata.

Dolerite blocks used to build the embankment retaining wall near the bridge.

Dipping Devonian strata near the footbridge over Benson's Brook.

We retraced our steps and continued on the Shropshire Way, pausing near the footbridge over Benson's Brook. Point F. (SO 5906 7721) We walked upstream of the footbridge. Richard pointed out that here we were seeing exposures of Devonian sediments showing quite a dip in the sandstones and mudstones. He said that the dip was due to the Caledonian Orogeny and was formed at the same time as the Ludlow Anticline.

Coarse grained pebbly sandstones in the barn wall at Nine Springs Farm.

We continued on the main footpath until we arrived at Nine Springs Farm. Point G. (SO 5911 7707). The stone barn walls adjacent to the farm contain a wide selection of local stone, showing different rock types including coarse grained pebbly sandstones. Some showed current bedding which were laid down as a part of the Coal Measures in a delta environment. Dolerite blocks could also be seen in the walls. LAGS examining the stone barn walls at Nine Springs Farm.

The Shropshire Way turned off to the right, but we carried straight on following the track along the bridle way until we rejoined the access road to Titterstone Clee. We then retraced our steps following the incline track back to Clee Hill village and the car park.

Richards initial assessment following the recce was: Clee Hill has a rather austere landscape but includes some spectacular geology and wonderful panoramic views of the surrounding countryside. In addition we saw some beautiful butterflies and plenty of bird life. All of this proved to be true, plus many notable wild flowers; in the event on a nice warm summers day the trail exceeded our expectations. It was a brilliant trail, breaking new ground for us with some challenging and unfamiliar geology, and maybe the first of many trails in the area. However, if you were to follow the trail on a gloomy winters day, it would paint an entirely different picture.

Once again our thanks go to Richard and Janet for organising the trail in an area with Carboniferous exposures. This was a new geological period for our group to experience. Richard gave detailed explanations on the formation of the Coal Measures and of the intrusion of the Dolerite sill. Janet pointed out many landscape features in the surrounding landscape for us to appreciate. Thanks also for their technical support in the preparation of this report.

Happy Trails.

Geological Maps...